Variable speed pulley



March l0, 1942. w. w. HALL-INAN VARIABLE SPEED PULLEY Original Filed Jan. l5, 1940 Patented Mar. l0, 1942 UNITEDSTATES- PATENT Aori-"ici:

v vanxatizslzlsgl) PULLEYV i l William W. llallinan,Mendota,lll.

Original application January 13, 1940, Serial No. Y 313,673. Divided and this application January 22, 1941, Serial No. 375,393-

(Cl. 'I4-230.17)

r n 14 Claims.

The present invention relates to variable speed pulleys, and is particularly concerned with variable speed pulleys controlled responsive to variations in' pressure or temperature, and adapted to provide a continuously and uniformly varying change of speed if used as a driven or driving r `March 15, 1938, for Variable speed pulleys, Patent No. 2,210,976, issued August 13, 1940.

The variable speed pulleys constructed according to the present invention are capable of many diierent applications. For example, they may be used for controlling the speed of a conveyor for conveying articles to be treated with heat, through a heated or drying atmosphere, or they may be used as a drive in a refrigerator system in which the temperature controls the speed of a compressor or a circulating fan.

One ofthe most important applications of my variable speed pulley as it now appears to me is in the application of the pulley to the circulation of air in heating or air conditioning systems. For example, according to the methods of the prior. art, air conditioning systems are provided with standard pulleys, the parts of which are manually adjustable, sov as to give the driven member a predetermined speed, and the pulleys on the motor and fan are so adjustedr relative to each other -to bring in sufllcient air to take care of the maximum heating load.

Under these conditions it is necessary to set the thermal control for the switch which controls will start to operate before the bonnet of the furnace has been heated to a sufllcient temperature to heat the air which is circulated by the fan.

Under these conditions of the prior art I have 'found that the fan matar starts and shuts off a number of 'times before itstarts to run regularly to circulate the air. For example, the fan Amotor is set at a lower temperature, the fan bonnet and thermal control and immediately `shuts the fan oi again. t

This is not a desirable mode of operation.

One of the objects of the present invention is the provision of an improved variable speed pulley and heating system, in which this intermittent action of the fan is eliminated, and in which it is not necessary to operate the furnace at such a high bonnet temperature. A lowering of the operating temperature is less wasteful of fuel, and more economical. y

Another object of the invention is the provi-i sion of an improved variable speed pulley and heating system, in which the furnace may be operated at a lower temperature and within a smaller range of temperature variation for the purpose of maintaining a more uniform temperature in the space to be supplied with heated air, and in order to operate the system more efficiently.

According to the practices of the prior art, furnaces which are provided with ordinary constant speed driving pulleys on their motors and circulating fans require a. heating to a temperature which is too high Afrom several points of view.

In such cases it is either necessary to have the i'an motor turned oi to stop circulation, when the furnace burner is turned oil, 4or the temperature will over-run that required if the fan con tinues to operate because the fan continues to use up the heat after the burner has stopped.

According to the present invention, the operation of the air and circulating fan is notwholly dependent upon the time of operation of the oil burner, as the air circulating fan may operate, depending upon the temperature in the bonnet, or'the temperature of the bonnet of the furnace, and there is n o tendency to over-run the temperature desired inthe rooms heated, because. the speed of operation of the circulating fan is continuously varied with the bonnet temperature, and diminishes as the temperature ofthe furnace bonnet or the air in the bonnet decreases.

I have found that air winch is warmer than the body temperature may actually feel cooler when it is subjected to circulation, on account of the tendency of the moving air to carry away the may start and run for a minute or so and then motor is started the cold air, which is brought in at the maximum pulley speed,` cools off the shut oi, for the reason that as soon as the fan vapors which are passed olf by the skin, and therefore it is not desirable to circulate air which is only slightly warmer than the body temperature at a 'high speed, as must be done with the systems of the prior art, where the fan speed is required to be set at a value which is suilicient -tc take case of the maximum heating load.

I have also found that air-which is at a temperature of from 100 degrees F. to 110 degrees F. still ieels warm when it is circulating at a relatively low speed, and there is no vcold air blast effect in my heating system which is operated under these conditions.

'l`herefore,another object of the invention is the provision of an improved heating system which is adapted to circulate the air at a speed and in a volume which is dependent upon the temperature of the circulating air so that blasts of air which feel cold may be avoided under all conditions and so that the circulation of the air in the system may be accomplished for a longer period of time and more nearly continuously to avoid stratification, or what is called a low sev. enty" at certain parts of the rooms which are being heated.

According to the present invention, with the improved thermally controlled variable speed pulley of my invention, the pulley may start at a slow speed, and the thermal control for the switch, which controls the fan motor, may be set relatively low, at, for example, from 100 degrees i?. to 110 degrees F.

This still feels Warm, as the fan is only moving a small volume ci air, but as the urnace heats up and the temperature of the air in the bonnet increases, the speed of the fan may be incerased by the thermally controlled pulley, so that heated air is taken away more rapidly from the furnace and the heat produced by the burner is distributed more quickly when. there is more heat to be' distributed.

Under these operating conditions the furnace may operate at a lower temperature and 'there will be less heat lost in the cellar and less heat lost up the furnace stack. For example, suppose there is an upstairs demand oi from 'to lll degrecs in the ritorni-ng, as there michi', be, this requires a greater temperature at the bonnet of i the furnace, the bonnet te-iperature may go up to 150 or l degrees present system xe blower speed t. en automat ically increased ,s the bonnet up. Another object of the presen* invention is provision of er. improved variable speed and heating s tern in which the speed ci opera* tion of the circuiating ian is incr-eased automat ically to compensate for any increased Filter resistance. The accomplishment of this result may be analyzed as follows:

The heat input of the furnace may be assumed t'o be constant, and the trensrer eectiveness of the furnace constant. increased lter resistance, which is caused by llipg up ci the lter with dust or other foreign material, permits less the eil air to pass through the lter and less heat is carried away from the bonnet. The furnace bonnet becomes hotter, and therefore the ther-` mostat, which controls the pulley according to the present invention, increases the eective diameter of the pulley, increases the speed of operation of the ian, and thus automatically cisets the increased lter resistance by a higher fan speed.

Another object of the invention is the provision of an improved heating system in which the circulating fan may continue to circulate'air at. .a low temperature continuously or almost continuously, so as to avoid stratication.

Another object of the invention is the provision of an improved thermally controlled variable speed fuel and heating system which is adaptable to heat anticipation controls. For example, I have foundthat the heat anticipation controls of the prior art will turn the burner on several times and then turn it ofi without the fan operating. This is not eiiicient because the heat which is produced during this intermittent operation of the burner, without ian operation, is not conveyed to the rooms to be heated.

One partial solution of s'uch a difculty would be the provision of a two-speed motor system, but such two-speed motor systems would be expensive anci at best provide only a partial solution of the difllculty.

Therefore, -another object of the invention is the provision of an improved thermally controlled variable speed pulley for heated air circulating systems, which provides a substantially continuous modulation of the ian speed, depending upon the temperature ofthe air to be circulated. Y

. The volume` of the blower increases with the square of the speed, 'and it is found that changes in volume may be m'ade practically proportional to changes in temperature so that the relation between volume and temperature may be represented, for all practical purposes, as a straight line curve.

Another object of the invention is the provision of a. thermostatically controlled variable speed pulley in which the thermostat rotates axially with the pulley, in order to eliminate pressure connections between rotating and non-rotating parts, and in which thrust bearings may be eliminated.

Another object of the invention is the provision of a thermostatically controlled variable speed pulley in which the thermostat acts against e. resilient separating force imposedby a wedge action oi a. belt to eliminate the need for springs in the pulley `structure or immediately associated therewith. l

Other objects and advantages of the inven-` tion will be apparent from the following descripU tion and the accompanying drawings, in which similar references indicate similar parts through.- out the several views.

Referring to the drawings, of which there is one sheet:

Fig. l is a diagrarrnnatic illustration of a heating system embodying a variable speed pulley constructed according to the present invention;

Fig. Z is an axial sectional view taken on the plane which passes through the axis of the pulley shaft, with the thermostat in elevation; and

Fig. 3 is a plan View taken from the top of Fig. 2.

Referring to Fig. 1, 2d indicates diagrammatically a heating system comprising a hot air furnace 2 i, provided with an outer housing 22, formlng a plenum chamber 2?,v and provided with a bonnet 24.

The plenum chamber is connected with the rooms to be heated by the usual cold air ducts 25, Awhich lead to the ventilation fan 26, prefer ably of the centrifugal typeI and the outlet ci the fan 26 is connected by a cold air duct Z'E to the plenum chamber 23.

yoke 6I is xedlysecured to the left pulley secof a pivoted motor mounting including the base 34 and the support 36.

In the embodiment illustrated, the base 34 of the motor 32 is pivotauy mounted at 3s on the support 36 so that the weight' of the motor tends to maintain the belt 33 under suitable tension.

The motor shaft 31 is provided with a thermostatically controlled variable diameter pulley, lndicated in its entirety by the numeral 36.

The thermostatic element 39 is subjected to heated air from the bonnet 24 by means of a conduit 46, which extends from the bonnet 24,

. the bonnet or placed inside of the bonnet, but

the present system is preferredbecause the motor maybe substantially isolated from the hottest parts of the furnace and kept in a cooler condition.

The' variable speed pulley 36 comprises a pair of movable pulley sections 42 and 43, one of which, 4,2, is fixedly secured to the motor shaft 31 by a key or a set screw 44 mounted in a thread-v ed bore 45.

The motor is preferably a substantially constant speed motor which would drive the fan 26 at a substantially constant speed, irrespective of the load on the fan. within certain predetermined limits.

The pulley section 42 may comprise a metal member made'of suitable material, such as steel. or it may, in some embodiments, be made of fibrous material.. such as moldedvphenolic condensation products.

The pulley section 42 is preferably provided with a centrally located cylindrical hub 46, having an axially extending cylindrical bore 41 for receiving the motor shaft 31.

At the left end in Fig. 2, the pulley-section may have a flat face 48, but on its right side and outside of the hub 46 it is provided with a frustoconical surface 49, forming Aone side of a substantially V shaped groove 66. v

The pulley section 43 may comprise a mem-y y rounding the cylindrical hub 63.

The cylindrical hub 63 may be provided with a cylindrical bore.54 for .slidably receiving and engaging the outer cylindrical surface of the hub 46 on the other pulley section.

tion 42.

' The hub 53 of the right pulley section is preferably provided with the axially extending slots 66 for slidably receiving the legs 62, 63 of the yoke 6I. The walls 61 and 66 ofslot 66 have a suitable tolerance with respect to the legs 62, 63 of the yoke 6|, to permit a sliding movement, and the pulley Section '43 is thus slidably mounted on the hub of the pulley section 42, but any su stantial amount of rotation is prevented between these pulley sections.

It will be noted that thehub 46 of the pulley section 42 is relatively long, providing an elongated cylindrical bearing surface 46 for the outer hub 63, so that there is very little possibility of any tilting of the pulley section 43 on the pulley section 42, due to the action of lV belt 33,` which usually engages over slightly more or slightly less than half of the pulley at one time.

'I'he belt 33, which has been'termed a V belt,

` is preferably substantially trapezoidal, in section,

being provided with the outer cylindrical surface 16, inner cylindrical surface 1l', and lateral cylinv dricalvsurfaces 12 and 1'3. Y

The axial dimension between the frusta-conical surfaces 12 and 13 is preferably relatively large so that these frusta-conical surfaces of the belt mayengage the surfaces 49 and 6I on the pulley sections over a wider range of movement of the pulley..

'I'he taper of the belt-engaging parts 49 and 5| of the pulley sections makes the engaging l' surfaces farther apart at larger eifective diamout this specication and claims'to include not The frusto-conical surface 49 and flat surface 2 48 of the section 42 may terminate in an annular ridge or at a cylindrical surface. 56, at the periphery'of the pulley section 42. In a similar manner there may be a cylindrical surface 66 at the periphery of the pulley section 43.

The hub 46 of the pulley section 42 may be provided with a pair of oppositely located and ber 6| has a bore 65 in each of its legs 62, 63 for receiving the screw bolts 69 and 66, whereby the only a belt of actual V cross-section, but a belt of the type illustrated, in which the-inner ridge of the v has been eliminated, so that the belt is actually trapezoidal in crossfsection.

The thermostatic controlling device 39 may consist of av metallic expansible bellows, having one end closed by a metallic supporting plate 16a. having a threaded supporting stud 1Ia The plate 10a has a. fluid-tight soldered or welded connection, with the end of the bellows 12a, and the stud 1Ia may have an axial filling` aperture 13a, which may be closed'after filling the bellows,

with a suitable expansible fluid by means of a drop of solder 14a.

Threaded stud 11a extends through a centrally located aperture 16 in the yoke 6I, and the bellows is xedly secured -to the yoke 6I by a clamping nut 16 and a lock nut11a. Thus the right end of the bellows is flxedly secured to the pulley section'42 through the intermediary of the yoke 6| and the hub 46 and screw bolts-59.

The opposite end of the bellows 12a is closed A by means of a metal plate 16, which is likewise .provided with a fluid-tight connection to the Thus a heating up of the expansible fluid inside l the bellows tends to force the Ypulley sections together and to increase the effective diameter of the pulley 38.

The yoke 6I may be provided with suitable permanent stops for limiting the spreading of the pulley sections 42, 43 by having the ends of the legs 62, 63 of reduced width to provide Vstop shoulders 82, 83. The device may also be. provided with suitable adjustable stop means, comprising a pair of sheet metal stop members 84, each of which are identical in shape and which are slidably mounted on the screw bolts 59 and 30 by means of slots 85.

AEach of these stop members 84 comprises a substantially rectangular strip of metal of the same width as the reduced width portions 86 of the legs 62 and 63. The stopmembers 84 may have laterally extending portions 81 at each side,

provided with depending guide flanges 88 at each side.

The guide anges 88 engage the sides of the legs 62, 63 and prevent rotation of the stop member 84 on screw bolt 59. The left edges 88 (Fig. 3) of the extensions 81 of the stop members 84 serve as stop surfaces for engaging the annular surface 90 at the right side of the plate 18 in Fig. 3` Thus the range of spread of the pulley sections 42 and 43 may be adjusted, and the device may be'used with smaller belts, that is, belts of less width in axial direction than that shown.

When the bellows is subjected to normal room temperatures or predetermined bonnet temperatures such as temperatures below which the motor 32 is not operated, the bellows is in a contracted position as shown in Fig. 2. The eiective diameter of the variable speed pulley 3| is then at a` minimum, and the sections 42, 43 of the pulley are automatically forced apart by the action of the wedge shaped belt 33, which is subjected to tension by a suitable tensioning device or by a tensioning weight as of the motor mount- 111g.

Upon heating up of the bellows 39, the bellows expands under the action of the expansible uid contained therein, and tends to force the pulley sections 42, 43 closer together from the position of Fig. 2 toward that of Fig. 3.

The effective pulley diameter is dependent upon the temperature to which the thermostats are subjected, and the taper of the belt-engaging surfaces on the pulley and the characteristics of the thermostats may be made such that the variation in speed is substantially proportional to the variation in temperature, by which I mean that the temperature speed relation may be expressed substantially as a straight line curve over a predetermined range of operation.

Upon a cooling down of the thermostat, the action of the belt and the belt-tensioning arrangement tends to force the pulley sections apart to follow up the contraction of the bellows and the eective diameter of the V pulley is at all times dependent upon the temperature lto which the thermostatic elements are subjected.

the pulley are in the position of Fig. 2, the effective diameter of the driving pulley is at a minimum, and the fan thus operated at a low speed, such as, for example, 275 R. P. M.

When the variable diameter pulley has its thermostatic element at or more than maximum temperature so that parts of the pulley are in the position shown in Fig. 3, the speed of rotation of the fan may be 500 R. P. M., for example. I desire it to be understood, however, that the speeds which are given for examples are not in any sense limits for practical use, as the ians speed may be made any desired value, and the examples given are merely to show the range which has been foundeilective in exemplary installations.

Although the air inthe bonnet is not at a high temperature, it still feels Warm as it emerges from the registers when the fan is moving only a small volume of air and at a low speed. Furthermore, the amount of air moved through the plenum chamber of the furnace is not such that it cools the furnace down too quickly, and the fan will continue to operate, instead of being turned off, as I have found to be the case with the devices of the prior art.

In the arrangements of the prior art I have frequently noted that the fan operating at a maximum speed passes so much cold air through the plenum chamber that the temperature is so reduced that the fan is turned off again. This intermittent action is eliminated by my invention. As the temperature of the air in the plenum chamber, and of course that discharged on the thermostat 39, by the duct 40, increases in temperature, the speed of the fan is automatically increased by the expansion of the thermostat and the increase in the effective diameter of the driving pulley.

'Ihe present heating system permits a continnous and gradual modulation of the fan speed so that the furnace may be operated at a lower The operation of the present variable speed y pulleys in a heating system of the type shown in Fig. l is as follows: When such pulleys are employed, the critical operating bonnet temperature 'for the thermostatic device controlling the fan temperature` and fuel may be saved. The fan may be operated over a longer range of time, or

it may be continuously operated at a lower rate of speed so as to avoid stratication and so as to constantly deliver heat from the furnace to the rooms by the moving air.

The speed varying effect of my thermostatically "controlled pulley may be accentuated by the use of a, belt of constant length and by having the driving and driven shafts at constant spacing, but by using a sectional spring-actuated pulley on the driven member, for taking up the'eiective length of the belt, which is increased or decreased, by the action of the thermostatic pulley. Thus, one pulley would increase in size, while the other decreased, and vice versa, accentuating the speed-changing effect of the thermostatically controlled pulley.

My thermostatically controlled pulley is adapted to be used either as the driving or the driven member, and its thermostatic element may be so arranged that it increases the diameter or decreases the diameter upon increasein temperature.

In addition to its use in a heating system as described, it may be used for controlling the speed of a conveyor for conveying articles through a heated atmosphere. Under such conditions, if the conveyor includes a large'number of painted articles, the temperature of the heated atmosphere would naturally drop, due to the absorption of the heat by the articles, and to the increased evaporation of the solvents of the paint.

Under these conditions, and with a decreased' temperature, the conveyor should move slower because the paint would require a longer time to dry at a lower temperature, and therefore the conveyo'r should keep the painted articles on the conveyor a longer period of time.

The same would be true in the case of a baking a straight-sided portion in slidable engagement oven, where my variable speed. pulley may be used Y for automatically compensating the conveyor drive for any' drops of temperature. The variable speed pulley may also be used in driving the fuel feed of a stoker, and it is of general application wherever the speed oi' drive may be advantageously varied responsive to temperature or pressure.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

l. In a variable diameter pulley, the combination 'of a pulley section adapted to be secured to a shaft or the like, with a second pulley section slidably mounted with respect to the iirst pulley section in an axial direction, said pulley sections being provided with opposed frusto conical surlfaces adapted to form a pulley groove of Wedgeshaped cross section, a frame carried by one of said sections in substantial dynamic balance therewith and-having a part oppositely disposed to the other of said pulley sections, a plate having slidable engagement with said frame in a direction axially of said pulley sections and adapted to engage said other pulley section, and' apressureresponsive bellows interposed between said oppositely disposed frame part and said plate, whereby expansion of said bellows is adapted to move one of 'said pulley sections relatively to the. other to vary the effective diameter 'of the pulley groove with respect to a wedge-shaped belt of constant width.

2. In a variable diameter pulley, the combination of a pulley section adapted to be secured to a shaft or the like, with a second pulley section v slidably mounted with respect to the rst pulley section in an axial direction, said pulley sections pressure responsive bellows interposed between said oppositely disposed frame part and said plate' whereby expansion of said bellows is adapted to move said plate and one of said pulley sections relatively to the other to vary the effective diameter of said pulley with respect to a belt of constant width.

3. In a variable diameter pulley, the combination of a pulley section adapted to be secured to a shaft or the like, with'a second pulley section slidably mounted with respect to the rst pulley section in an axial direction, said pulley sections withsaid frame to prevent relative rotative movement between said pulley sections, and a pressure responsive bellows interposed between said oppositely disposed'frame part and said other pulley section whereby expansion of said bellows is adapted to move one of said pulley sections relatively to the other to vary the effective diameter of the pulley vgroove with respect to a wedgeshaped belt of constant width.

4. In a variable diameter pulley for use with a tensioned wedge-shaped belt of constant width, a, pulley section adapted to be secured `to a shaft or the like, a second pulley section slidably mounted with respect to the first pulley section in an-J axial direction, said pulley sections being provided with opposed frusto-conical surfaces adapted to form a, pulley groove of Wedge-shaped crossj section, a straight-sided framecarried by one of said sections and having a part oppostely disposed to the other of said pulley sections, the other of said pulley sections. having a straightsided portion for slidably receiving' said frame to prevent relative rotative movement between said pulley sections, an adjustable'stop mounted to limit the slidable .movement separating said pulley sections, and a pressure responsive bellows' interposed between said opp ositely disposed frame part and said other pulley section whereby expansion of said bellows is adapted to move one of said pulley sections relatively to the other against the'action of said tensioned wedge belt to increase tion slidably mounted with respect to the first the eiective diameter of the pulley groove with respect to said belt.

5. In a variable diameter pulley, the combination of a pulley section adapted to be secured yto a shaft or the like, with a second pulley secpulley section in an axial direction, said pulley sections being provided with opposed frustoconical surfaces adapted to form a pulley groove of wedge-shaped cross section, a frame carried by one of said sections in substantial dynamic balance therewith, the other pulley section than' that carrying the frame having a part projecting beyond the pulley section carrying the frame, and a pressure-responsive bellows mounted concentrically with the pulley. sections and interposed between the frame and the other pulley section, whereby expansion of the bellows is adapted to move the other pulleysection relatively t the pulley section carrying the frame to vary the effective diameter of the pulley groove with respect to a wedge-shaped belt of constant width. 6. In a variable diameter pulley, the combination of a pulley section adapted to be secured to a shaft or the like, with a second pulley section slidably mounted with' respect to the iirst pulley section in an axial direction, said pulley sections being provided with opposed frustoconical surfaces adapted to form a pulley groove of Wedge-shaped cross section, a frame carried by one of said sections in substantial dynamic balance therewith, the frame having an'o-ppositely disposed part coaxial with the pulley sections, the other pulley section than that carrying the frame having a part in slidable engagement with the frame in a direction atrially of the pulley sections and projecting axially beyond the pulley section carrying the frame, and a heat-responsive bellows positioned between the oppositely disposed frame part and the projecting pulley part, whereby expansion ofthe bellows is adapted to move the extending pulley section relatively -to the frame and to the other pulley section to vary the effective diameter of the pulley groove with respect to a wedge-shaped belt of constant width.

7. In a variable diameter pulley, the combination of a pulley section adapted to be secured to a shaft or the like, with a second pulley section slidably mounted with respect to the'rst pulley section in an axial direction, said pulley sections being provided with opposed frusto-conical surfaces adapted to form a pulley groove of wedge-shaped cross section, a frame carried by one of said sections in substantial dynamic balance., therewith and having a part oppositely disposed to the other pulley section, guide means carried by the other pulley section adjacent the frame to embrace said frame, the guide means being normally spaced from the frame to provide an operating clearance, and a. pressure-responsive bellows interposed between the oppositely disposed frame part and the other pulley section, whereby expansion of the bellows isadapted to move the other pulley section relative 'to the section carrying the frame to vary the effective diameter of said pulley with respect to a belt of constant width. v

8. In a variable diameter pulley, the combination of a pulley section comprising a substantially cylindrical hub, and a radially extending flange having a'frusto-conical surface for entubular extension having an axially vextending groove, a' U-shaped metal frame member having a pair of legs secured to said hub, and an expansible bellows carried by said U-shaped frame member, and adapted to act on said axial extension oi said second section.

9. In a variable diameter pulley, the combination of a pulley section comprising a substantially cylindrical hub, and a radially extending flange having a frusto-conical surface for engaging one side of a V-belt, said hub having a bore for receiving a shaft, with means for securing said hub to a shaft, a second pulley section comprising an annular metal member having a radially extending flange similar to the first mentioned flange, and having an oppositely extending frusto-conical surface for engaging the other side of a V-belt, said second pulley section being slidably mounted on said hub, and having a tubular extension surrounding said hub and adapted to project beyond said hub, said tubular extension having an axially extending groove, a U-shaped metal frame member having a pair of legs secured to said hub, and an expansble bellows carried by said U-shaped frame member, and adapted to act on said axial extension of said second section, said bellows having a pressure plate mounted on one end adjacent said hub,

' and said pressure plate extending radially beyond said hub to engage said axialL extension of said second section.

10. In a variable diameter pulley, the combination of a pulley section comprising a substantially cylindrical hub, and a radiallyextending flange having afrusto-conlcal surface for engaging one side of a V-belt, said hub having a bore for receiving a shaft, with means for securing said hub to a shaft, a second pulley section comprising an annular metal member having a radially extending flange similar to the rst mentioned flange, and having an oppositely extending frusto-conical surface for engaging the other side of a V-belt, said second pulley section being slidably mounted on said hub, and having a tubular` extension surrounding said hub and adapted to project beyond said hub, said tubular extension having anaxially extending groove, a U-shaped metal frame member having a pair of legs secured to said hub, and an expansibleA bellows carried by said U-shaped frame member, and adapted to act on said axial extension of said second section, said U-shaped frame having one of its legs extending into said axially extending groove for preventing relative rotation between said second section and said hub.

11. In a variable diameter pulley, the combination of a pulley section comprising a substantially cylindrical hub, and a radially extending flange having a truste-conical surface for engaging one side of a V-belt, said hub having a bore for receiving a shaft, with means for securing said hub to a shaft, a second pulley section comprising an annular metal member having a 4radially extending flange similar to the first mentioned flange, and'having an oppositely extending frusto-conical surface for engagingv the other` side of a V-belt, said second pulley section being slidably mounted on said hub, and having a tubular extension surrounding said hub and adapted to project beyond said hub, saidl tubular extension having an axially extending groove, a U-shaped metal frame member hav` ing a pair of legs secured to said hub, and an expansible bellows carried by said U-shaped frame member, and* adapted to act on said axial extension of said second section, said bellows being provided at one end with a supporting plate secured thereto, and having an axially extending threaded member, said frame having an aperture, and said bellows having its threaded member secured in said aperture.

l2. In a variable diameter pulley, the combination of a pulley section comprising a substantially cylindrical hub, and a radially extending flange having a frusto-conical surface for engaging one side of a V-belt, said hub having a -bore for receiving a' shaft, with means for securing said hub to a shaft, a second pulley section'comprisingan annular metal member hav ing a radially extending flange similar to the first mentioned flange, and having an oppositely extending frusto-conical surface for engaging the other side of a V-belt, said second pulley section being slidably mounted on said hub, and having a tubular extension surrounding said hub and adapted to project beyond said hub. said tubular extension having an axially extending groove, a U-shaped metal frame member having a pair of legs-secured to said hub, and an expansible bellows carried by said U-'shaped frame member, and adapted to act on said axial extension of said second section, said bellows besaid bellows, and said through bore being closed nation of a pulley section comprising a substantially cylindrical hub, and a radially extending flange having a frusta-conical surface for engaging one side of a V-belt, said -hubvhaving a bore for receiving a shaft, with means for securing said hub to a shaft, a second pulley section comprising an annularv metal member having a radially extending ange similar to the first mentioned ange, and having an oppositely extending frusto-conical surface for engaging the other side of a V-belt, said second pulley section being slidably mounted on said hub, and havinga tubular extension surrounding said hun and adapted to project beyond said hub, said tubular extension having an axially extending groove, a U-shaped metal frame member having a pair of legs secured to said hub, and an expansible bellows carried by vsaid U-shaped frame member, and adapted to act on said axial extension of said second section, said bellows having a vpressure plate mounted on one end adjacent seid hub, and said pressure plate extending radiauy beyond'said hub to engage' said .axial ex.- tension of said second section, said bellows being tlxedly secured at one end to said trame. and

said pressure plate having grooves for-slidably engaging said frame at its other end.

14. In a variable diameter pulley, the combination of a pulley section comprising a substan-y tially cylindrical hub, and a radially extending ange having a truste-conical surface for e'ngaging one side oi a V-belt, said hub having a bore for receiving a shaft, with means for securing said hun to a shaft, a second pulley section comprising an annular metal member havlng a radially extending iiange similar to the first mentionedy dange, and having an oppositely extending truste-conical surface for engaging the other side ci a V-belt, said second pulley section being slidably mounted on said hub, and having a tubular extension surrounding said hub and apted to project beyond said hub, said tubular extension having an axially extendlng groove, a U-shaped metal frame member having e. pair of legs secured to said hub, and an expansible bellows carried by said U-shaped frame member, and adapted to act on said axial extension of said second section, and adjustable stop means carried by said'hub, and adapted to limit the spreading movement oi said pulley sections. 

